15
A Comparative Orthognathic Cephalometric Study Among
Saudi, African-American and Japanese Adults: Hard Tissue Measurements
Laila F. Baidas1 and Sahar F. Al-Barakati2
1Assistant Professor, Orthodontics, College of Dentistry, King Saud University, Riyadh, Saudi Arabia E-mail: [email protected]
2Associate Professor, Orthodontics, College of Dentistry, King Saud University, Riyadh, Saudi Arabia E-mail: [email protected]
(Received 4/4/2009; accepted for publication 6/10/2009)
Keywords: Burstone analysis, Hard-tissue measurements, Orthognathic surgery, Saudi adult, Black American adult, Japanese adult, Comparison, Ethnic difference.
Abstract. The purpose of the present investigation was to compare hard tissue analysis obtained from Saudi adults with reference data of Japanese and African-American adults in order to determine the differences of the hard tissue analysis between different ethnic groups. Sixty-two lateral cephalometric radiographs were collected from the archives of cephalometric radiograph files taken by dental students of King Saud University, College of Dentistry (31 females and 31 males), age range was 22-24 years. The lateral cephalometric radiographs were analyzed and the mean values of hard and dental measurement were compared with those of African-American adults, and the Japanese adults. The results showed Saudi males compared to Black had significantly: increased anterior cranial base, and reduced posterior cranial base, reduced facial convexity, maxillary protrusion, and maxillary length. Saudi adult females had smaller upper posterior facial height and lower anterior facial height, downward tipping of maxilla, smaller vertical dental heights, reduced total mandibular body length, and less proclination of lower incisors. Saudi adults compared to Japanese had significantly: increased anterior cranial base, reduced posterior cranial base, prognathic maxilla, prominent chin, smaller vertical lower dental heights, smaller ramus and obtuse gonial angle in males, less proclination of upper and lower incisors, and less steep occlusal plane to horizontal plane.
This study may be useful in providing racially specific cephalometric values for diagnosis and treatment planning for orthognathic surgery of Saudi adults. It might represent true differences in skeletal and dental features between the three racial groups.
Introduction
The term "ethnic group" refers to a population or nation with a common bond such as a geographical boundary, a cultural or language, or being racially or historically related (Barnhart, 1953). In a multicultural society, racial and ethnic differences are assuming an increasing level of importance. It brings with it the need to recognize that single standard norms may not be appropriate when making diagnostic and treatment planning decisions for a patient from diverse racial and ethnic backgrounds.
Races are classified into three groups: Asiatic (Mongoloid), Black (Negroid) and White (or Caucasian) (Montague, 1942; Coon et al., 1950).
Each group has its own characteristics to distinguish them from each other. Furthermore, within the same race, subgroups have their own characteristics
(Burstone, 1958; Holdaway, 1983). Arabs are considered as a subgroup of Caucasian (Coon et al., 1950).
Cephalometric norms for Saudi Arabians were studied since 1987 until today using different cephalometric analyses. Sarhan and Nashashibi (1988) compared cephalometric norms for Saudi boys aged from 9-12 years with a British sample with same age. The Saudi boys demonstrated a slightly prognathic-faces, more protrusive upper and lower incisors, and low gonial and saddle angles.
Nashashibi et al. (1990) found that Saudi boys had a more protrusive maxillary apical base and double dental protrusion. Al-Jasser (2005) compared cephalometric norms of Saudis and European- Americans using Downs and Steiner analysis. He found normal Saudis have slightly protrusive maxillas, a tendency to Class II facial pattern, and a
norms using McNamara's analysis, with European American norms. Their results showed the Saudis have a greater convex profile with reduced chin prominence, steeper mandible and more bimaxillary protrusion. Al-Barakati and Baidas (2009) conducted a cephalometric study on a sample of Saudi dental students using Burstone analysis. They concluded that Saudi had an increase in cranial base length; the mandible was more posterior to maxilla, increase in mandibular plane angle, backward rotation of the mandible, less prominent chin, shorter maxillary length, and also less proclination of lower incisors than the Burstone sample.
Maxillofacial and oral surgeons and orthodontists currently treat an increasing number of patients needing orthognathic surgical procedures. The cephalometric analysis for orthognathic surgery of Burstone et al. (1978) was especially adapted to the diagnosis and treatment planning for orthognathic surgery cases because it was based largely upon rectilinear measurements that can be used at surgery.
Normal values for cephalometric analysis for orthognathic surgery have been developed for white American (Burstone et al., 1978), Japanese (Alcalde et al., 1998), and American black (Flynn et al., 1989). Further, Connor and Moshiri (1985) and Flynn et al. (1989) showed that the cephalometric measurements established for North Americans using Burstone analysis (Burstone et al., 1978) were at variance to those measurements found in a black South African population group. Furthermore, Miyajima et al. (1996), Alcalde et al. (1998)and Ioi et al. (2007) found fundamental variations exist in the craniofacial structure of Japanese and European- Americans. Accordingly, Surgical and orthodontic cephalometric analyses developed for one population have been shown to be inadequate for other racial groups. Therefore, the purpose of the present investigation was to compare cephalometric hard tissue measurements of orthognathic surgery between Saudi Arabian adults (Al-Barakati and Baidas, 2009) to Japanese adults (Alcalde et al., 1998) and to Black American (Flynn et al., 1989) adults in order to determine the dento-skeletal differences among them based on Burstone analysis (Burstone et al., 1978).
Material and Methods
Sixty-two lateral cephalometric radiographs of Saudi subjects (31 females and 31 males) with a mean age of 23 ± 1 year were analyzed. These
dental students used as part of their undergraduate orthodontic course requirements at College of Dentistry, King Saud University (the students were informed about their rights to take the radiographs).
The inclusion criteria of sample were:
‐ A pleasing and balanced facial profile with competent lips.
‐ Class I molar and canine relationship.
‐ Normal overjet (1-4 mm).
‐ Normal overbite (35-50%).
‐ Average skeletal relationship (ANB = 1-4.5°).
‐ No obvious craniofacial deformities.
‐ No previous orthodontic treatment.
All lateral cephalometric radiographs were taken in maximum intercuspation with head in natural head position and lips in repose. Each radiograph was scanned into a digital format using Epson® perfection 4990 photo scanner (Seiko Epson Corporation, Nagano, Japan), and was digitized by the same examiner in a darkened room using specific points required by the software. Linear and angular measurements according to Burstone analysis (Burstone et al., 1978) were calculated electronically using the Dolphin® version 10 software (Dolphin Imaging and Management Solutions, Chatsworth, Calif., USA) and recorded in print out. The computer analysis software was adjusted for the magnification factor using two points on the radiograph at a distinct distance.
The published data for Japanese (Alcalde et al., 1998) and African-American (Flynn et al., 1989) adults were used as the reference sample for the purpose of comparison with Saudi adults. Hard tissue landmarks and reference lines of Burstone et al. (1978) analysis were illustrated in Fig. 1. From the digitized points, 6 angular and 17 linear measurements were obtained (Table 1) (Figs. 1, 2 and 3).
Error of the method
The error of the method was performed using coefficient of reliability (Guilford and Fruchter, 1984) by repeated measurements of 15 cephalometric radiographs in two week interval by the same examiner to determine the error of the measurement method. The coefficient of reliability was calculated as follows: coefficient of reliability=1- (Se2÷St2), where Se2 is the variance due to random error, and St2 is the total variance of the measurements, and it is indicated that the measurements were highly correlated and ranged between 0.99 and 0.95.
Fig. 1. The major landmarks and reference planes used in Burstone et al. analysis:
Nasion (N), sella (S), anterior nasal spine (ANS), posterior nasal spine (PNS), pterygomaxillary fissure (PTM), point A (A), point B (B), pogonion (PG), gnathion (GN), menton (ME), gonion (GO), articular (AR), mesiobuccal cusp tip of upper first molar (UMT), mesiobuccal cusp tip of lower first molar (LMT).
The reference planes: Mandibular plane (MP), Nasal floor plane (NF), Horizontal plane (HP) a line 7° from SN plane, Occlusal Plane(OP) a line from buccal groove of both 1st molars through a point 1mm apical of incisal edge of lower central incisor
Fig. 2. Cranial base length and vertical skeletal measurements:
1; Posterior cranial base length(AR-PTM), 2; Anterior cranial base length (PTM-N), 1 + 2; total cranial base length, 3; Upper anterior facial height (N-ANS), 4;
Lower anterior facial height (ANS-GN), 5; Upper posterior facial height (PNS-N), 6; Mandibular plane angle (MP-HP).
Fig. 3. Vertical dental and Maxilla/Mandible measurements:
1; Upper anterior dental height (U1-NF), 2; Lower anterior dental height (L1-MP), 3; Upper posterior dental height (UM-NF), 4; Lower posterior dental height (LM– MP), 5; Maxillary length (PNS-ANS), 6;
Chin depth (B-PG), 7; Gonial angle (AR-GO-GN).
Error of the method
The error of the method was performed using coefficient of reliability (Guilford and Fruchter, 1984) by repeated measurements of 15 cephalometric radiographs in two-week interval by the same examiner to determine the error of the measurement method. The coefficient of reliability was calculated as follows: coefficient of reliability=1- (Se2÷St2), where Se2 is the variance due to random error, and St2 is the total variance of the measurements, and it is indicated that the measurements were highly correlated and ranged between 0.99 and 0.95.
Statistical analysis of data
Data transferred to the computer for analysis using SPSS program for Windows (version 12 SPSS Inc., Chicago, IL, USA). Descriptive statistics (mean, standard deviation) were employed for each variable in both sexes separately. The significant difference of the mean values between the Saudi males, females and other ethnic groups, Japanese and African- American adults was tested using independent student's t- test at 5% level (P < 0.05).
Results
The results comparing of the hard tissue (skeletal and dental) cephalometric values in Saudi, African- American, and Japanese groups for both sexes are presented in Tables 2, 3, 4 and 5.
1. Posterior cranial base (Ar-PTM mm): A distance from Ar to PTM, parallel to Hp.
2. Anterior cranial base (PTM-N) mm: A distance from PTM to N, parallel to Hp.
Horizontal Skeletal Relationship:
3. Facial convexity (N-A-Pg): An angle formed by the line N-A and the line A-pg.
4. Maxillary protrusion (N-A) mm: A distance from point A to perpendicular line from N, parallel to Hp.
5. Mandibular protrusion (N-B) mm: A distance from point B to perpendicular line from N, parallel to Hp.
6. Chin protrusion (N-Pg) mm: A distance from pogonion to a perpendicular line from N, parallel to Hp.
Vertical Skeletal Relationship:
7. Upper anterior facial height (N-ANS) mm: A distance from N to ANS, perpendicular to Hp.
8. Lower anterior facial height (ANS-Gn) mm: A distance from ANS to Gn, perpendicular to Hp.
9. Upper posterior facial height (PNS-N) mm: A perpendicular distance from Hp to PNS.
10. Mandibular plane angle (MP-HP): An angle formed between Go-Gn line and Hp.
Vertical Dental Relationship:
11. Upper anterior dental height (U1-NF) mm: A perpendicular line from the incisal edge of upper incisor to NF.
12. Lower anterior dental height (L1-MP) mm: A perpendicular line from the incisal edge of lower incisor to MP.
13. Upper posterior dental height (UM-NF (mm): A perpendicular line from the mesiobuccal cusp tip of upper first molar to NF.
14. Lower posterior dental height (LM– MP) mm: A perpendicular line from the mesiobuccal cusp tip of lower first molar to MP.
Maxilla and Mandible:
15. Maxillary length (PNS-ANS) mm: A distance from PNS to ANS, parallel to Hp.
16. Mandibular ramus length (Ar-Go) mm: A line from Ar to Go.
17. Mandibular body length (Go-Pg) mm: A distance from Go to Pg.
18. Chin depth (B-Pg) mm: A distance from B point to a perpendicular line to MP through Pg.
19. Gonial angle (Ar-Go-Gn): An angle between ramal length and MP.
Dental Relationship:
20. Occlusal plane angle (OP – Hp): An angle between OP and HP.
21. Wits analysis (A-B/OP) mm: Two perpendicular lines from points A and B to OP.
22. Upper incisor inclination (U1-NF): An angle between the lines from the upper incisal edge through the tip of the root to NF.
23. Lower incisor inclination (L1-MP): An angle between the lines from the lower incisal edge through the tip of the root to MP.
Table 2. Statistical comparison between adult Saudi and African-American males Saudi male
no = 30
African male no = 15
Components No. Variables
mean SD mean SD
t-value P-value Sig. level 1 Ar-PTM 33.874 3.240 41.100 3.900 6.213 0.000 ∗∗∗
Cranial base
2 PTM-N 57.610 4.420 51.500 3.100 5.419 0.000 ∗∗∗
3 N-A-PG 3.168 5.183 9.900 6.300 3.592 0.002 ∗∗
4 N-A(HP) -0.848 4.998 3.200 3.400 3.224 0.005 ∗∗
5 N-B(HP) -6.290 7.152 -3.500 6.700 1.295 0.404 NS Horizontal skeletal relation
6 N-PG -4.871 7.378 -4.200 7.900 0.276 1.568 NS 7 N-ANS 56.297 2.884 55.800 2.600 0.586 1.122 NS 8 ANS-GN 70.481 4.198 74.500 10.900 1.380 0.349 NS 9 PNS-N 55.577 3.021 57.400 3.200 1.844 0.144 NS 10 MP-HP 27.006 3.766 25.400 6.700 0.865 0.784 NS 11 UI-NF 29.890 2.803 32.700 3.700 2.602 0.025 ∗ 12 U6-NF 25.326 1.812 27.100 1.800 3.127 0.006 ∗∗
13 L6 -MP 31.097 3.310 39.600 2.600 9.482 0.000 ∗∗∗
Vertical skeletal and dental
14 L1-MP 41.342 3.290 50.800 3.600 8.587 0.000 ∗∗∗
15 PNS-ANS 53.923 3.600 58.800 3.900 4.076 0.000 ∗∗∗
16 AR-GO 51.371 5.380 53.500 4.400 1.427 0.321 NS 17 GO-PG 82.119 4.860 87.300 6.900 2.611 0.025 ∗ 18 B-PG 6.923 1.662 5.900 2.800 1.307 0.396 NS Maxilla and mandible
19 AR-GO-GN 123.265 6.136 120.000 8.900 1.281 0.414 NS 20 OP-HP 6.152 3.971 5.400 4.300 0.570 1.144 NS 21 UI-NF 111.490 6.517 111.300 8.500 0.077 1.879 NS 22 L1/GO-ME 91.242 5.979 97.700 6.000 3.426 0.003 ∗∗
Dental relationships
23 A-B(//OP) -0.558 2.487 -2.500 5.100 1.397 0.339 NS
∗P <0.05 ∗∗P <0.001 ∗∗∗P <0.0001
Table 3. Statistical comparison between adult Saudi and African-American females Saudi female
no = 30
African female no = 18
Components No. Variables
mean SD mean SD
t-value p-value Sig. level 1 Ar-PTM 29.432 3.421 37.200 4.000 6.903 0.000 ∗∗∗
Cranial base
2 PTM-N 52.297 4.056 49.900 4.200 1.950 0.114 NS 3 N-A-PG 4.881 4.568 10.400 5.500 3.598 0.002 ∗∗
4 N-A(HP) 0.119 3.820 3.500 4.000 2.899 0.011 ∗ 5 N-B(HP) -5.239 6.126 -2.600 7.200 1.305 0.397 NS Horizontal skeletal relation
6 N-PG -4.223 7.346 -3.300 8.400 0.388 1.400 NS 7 N-ANS 50.890 3.318 52.700 3.000 1.957 0.113 NS 8 ANS-GN 62.619 4.924 69.300 6.500 3.777 0.001 ∗∗
9 PNS-N 49.800 2.710 53.100 3.200 3.676 0.001 ∗∗
10 MP-HP 27.790 5.584 25.300 6.200 1.405 0.333 NS 11 UI-NF 27.968 2.950 31.100 3.900 2.952 0.010 ∗ 12 U6-NF 22.806 2.367 25.000 2.900 2.725 0.018 ∗ 13 L6 -MP 28.171 3.087 35.500 3.300 7.673 0.000 ∗∗∗
Vertical skeletal and dental
14 L1-MP 37.468 3.526 45.000 4.600 5.999 0.000 ∗∗∗
15 PNS-ANS 50.326 3.753 56.400 3.800 5.419 0.000 ∗∗∗
16 AR-GO 45.355 4.127 48.100 3.700 2.398 0.041 NS 17 GO-PG 75.632 6.117 84.300 4.600 5.616 0.000 ∗∗∗
18 B-PG 6.119 1.394 5.100 1.900 1.987 0.106 NS Maxilla and mandible
19 AR-GO-GN 122.577 5.948 119.100 5.400 2.093 0.084 NS 20 OP-HP 7.877 4.313 8.600 5.100 0.505 1.231 NS 21 UI-NF 112.594 6.233 115.200 6.100 1.430 0.318 NS 22 L1/GO-ME 92.735 6.745 103.200 6.600 5.307 0.000 ∗∗∗
Dental relationships
23 A-B(//OP) 0.152 2.295 0.300 2.800 0.191 1.699 NS
∗P <0.05 ∗∗P <0.001 ∗∗∗P <0.0001
Table 4. Statistical comparison between adult Saudi and Japanese males Saudi male
no = 30
Japanese male no = 98
Components No. Variables
mean SD mean SD
t-value P-value Sig. level 1 Ar-PTM 33.874 3.240 37.600 2.800 5.758 0.000 ∗∗∗
Cranial base
2 PTM-N 57.610 4.420 51.600 3.700 6.849 0.000 ∗∗∗
3 N-A-PG 3.168 5.183 4.240 5.300 0.998 0.640 NS 4 N-A(HP) -0.848 4.998 -1.960 4.700 1.095 0.552 NS 5 N-B(HP) -6.290 7.152 -7.900 7.300 1.087 0.558 NS Horizontal skeletal relation
6 N-PG -4.871 7.378 -8.000 8.600 1.975 0.101 NS 7 N-ANS 56.297 2.884 58.600 3.500 3.672 0.001 ∗∗
8 ANS-GN 70.481 4.198 68.800 4.900 1.863 0.129 NS 9 PNS-N 55.577 3.021 55.600 2.900 0.037 1.942 NS 10 MP-HP 27.006 3.766 25.200 5.400 2.079 0.079 NS 11 UI-NF 29.890 2.803 30.080 2.930 0.325 1.492 NS 12 U6-NF 25.326 1.812 25.900 2.300 1.436 0.307 NS 13 L6 -MP 31.097 3.310 37.700 2.500 10.222 0.000 ∗∗∗
Vertical skeletal and dental
14 L1-MP 41.342 3.290 45.300 3.100 5.918 0.000 ∗∗∗
15 PNS-ANS 53.923 3.600 54.500 3.800 0.768 0.888 NS 16 AR-GO 51.371 5.380 54.200 4.600 2.638 0.019 ∗ 17 GO-PG 82.119 4.860 80.950 4.900 1.165 0.492 NS 18 B-PG 6.923 1.662 7.010 1.800 0.250 1.606 NS Maxilla and mandible
19 AR-GO-GN 123.265 6.136 117.900 6.050 4.257 0.000 ∗∗∗
20 OP-HP 6.152 3.971 8.700 5.020 2.912 0.008 ∗∗
21 UI-NF 111.490 6.517 116.350 6.600 3.608 0.001 ∗∗
22 L1/GO-ME 91.242 5.979 95.090 6.670 3.035 0.006 ∗∗
Dental relationships
23 A-B(//OP) -0.558 2.487 0.400 3.160 1.745 0.167 NS
∗P <0.05 ∗∗P <0.001 ∗∗∗P <0.0001
Saudi – African-American comparison
Cephalometric standards and student's t-test results for the Saudi male and African-American male samples are summarized in Table 2. The results show that 11 out of 23 variables had significant differences at (P < 0.01). Posterior cranial base (AR- PTM) was much smaller in Saudi adult male than in the African-American (P < 0.0001), whereas the anterior cranial base (PTM-N) was notably larger in Saudi adult male (P < 0.0001). No major difference was observed in the total cranial base length (N-AR).
Burstone et al. (1978) had described the total cranial base length as a relatively stable anatomical plane, and sum of the anterior and posterior base lengths.
Among horizontal skeletal relation, skeletal facial convexity (N-A-PG) and maxillary protrusion were considerably smaller in the Saudi male group compared with the African-American male (P <
0.002, and P < 0.005, respectively). Upper anterior dental height (UI-NF), upper posterior dental height (U6-NF), lower anterior dental height (L1-MP), and lower posterior dental height (L6-MP) were significantly smaller in Saudi adult male (P < 0.02, P < 0.006, and P < 0.000 respectively). Saudi male subjects had a significantly smaller maxillary length (PNS-ANS) and the mandibular body length (GO- PG). African-American male subjects had significantly more protruded lower incisors (L1/GO- ME) compared with Saudis.
Cephalometric standards and student's t-test results for the Saudi female and African-American female samples are summarized in Table 3. Thirteen out of 23 variables had significant differences at (P < 0.01). Posterior cranial base (AR-PTM) was significantly smaller in Saudi adult female than in the African-American (P < 0.0001). Consequently, total cranial base length (N-Ar) was smaller in Saudi female. Skeletal facial convexity (N-A-PG) and maxillary protrusion (N-A) were considerably smaller in the Saudi female group compared with the African- American female (P < 0.002, and P < 0.01 respectively). At the same time, the Saudi adult female had smaller lower anterior facial height (ANS-Gn) and upper posterior facial height (PNS-N) than African- American female (P < 0.001). Upper anterior dental height (UI-NF), upper posterior dental height (U6-NF), lower anterior dental height (L1-MP), and lower posterior dental (L6-MP) were significantly smaller in Saudi adult female (P < 0.01, P < 0.01, and P < 0.000, respectively). Saudi female subjects had a significantly smaller maxillary base length (PNS-ANS). The mandibular body length (GO-PG) was smaller in Saudi adult females (P < 0.000). The gonial angle (AR-Go- Gn) was larger in Saudi female than African-American but it was not significant. The only significantly different dental relationship between Saudi and African-American females was that Blacks had greater lower incisor proclination (L1/GO-ME).
mean SD mean SD
1 Ar-PTM 29.432 3.421 34.300 2.800 7.311 0.000 ∗∗∗
Cranial base
2 PTM-N 52.297 4.056 47.900 3.200 5.599 0.000 ∗∗∗
3 N-A-PG 4.881 4.568 5.600 6.100 0.724 0.940 NS 4 N-A(HP) 0.119 3.820 -1.980 4.000 2.699 0.016 ∗ 5 N-B(HP) -5.239 6.126 -8.100 6.900 2.255 0.051 NS Horizontal skeletal relation
6 N-PG -4.223 7.346 -9.100 8.100 3.222 0.003 ∗∗
7 N-ANS 50.890 3.318 53.700 3.000 4.281 0.000 ∗∗∗
8 ANS-GN 62.619 4.924 63.800 4.900 1.190 0.472 NS 9 PNS-N 49.800 2.710 51.600 2.600 3.321 0.002 ∗∗
10 MP-HP 27.790 5.584 27.080 6.200 0.616 1.077 NS 11 UI-NF 27.968 2.950 28.500 2.790 0.905 0.734 NS 12 U6-NF 22.806 2.367 23.600 2.300 1.672 0.193 NS 13 L6 -MP 28.171 3.087 34.200 2.700 9.931 0.000 ∗∗∗
Vertical skeletal and dental
14 L1-MP 37.468 3.526 41.700 3.300 6.030 0.000 ∗∗∗
15 PNS-ANS 50.326 3.753 50.100 3.300 0.306 1.521 NS 16 AR-GO 45.355 4.127 47.050 4.500 1.998 0.095 NS 17 GO-PG 75.632 6.117 75.600 4.500 0.027 1.956 NS 18 B-PG 6.119 1.394 6.100 1.600 0.067 1.894 NS Maxilla and mandible
19 AR-GO-GN 122.577 5.948 119.700 7.200 2.291 0.047 NS 20 OP-HP 7.877 4.313 10.800 4.800 3.281 0.003 ∗∗
21 UI-NF 112.594 6.233 114.700 6.900 1.638 0.207 NS 22 L1/GO-ME 92.735 6.745 94.320 6.990 1.156 0.499 NS Dental relationships
23 A-B(//OP) 0.152 2.295 1.300 3.050 2.306 0.045 NS
∗P <0.05 ∗∗P <0.001 ∗∗∗P <0.0001
Saudi – Japanese comparison
Table 4 presented cephalometric standards and student's t-test results for the Saudi male and Japanese male subjects. Posterior cranial base (Ar-PTM) was much smaller in Saudi adult male than in the Japanese (P < 0.0001), whereas the anterior cranial base (PTM-N) was notably larger in Saudi adult male (P < 0.0001). Saudi male group had reduced upper anterior facial height (N-ANS), lower anterior dental height (L1-MP), and lower posterior dental (L6–MP) compared to Japanese (P < 0.001 and P < 0.000, respectively). Mandibular ramus height (AR-Go) was smaller in Saudi male subject (P < 0.019). However, the gonial angle (AR-GO-GN) was significantly larger in Saudi than Japanese male subjects (P < 0.000). There are significantly different dental relationships between Saudi and Japanese males.
Saudi had less proclination of upper and lower incisor (UI-NF, L1/GO-ME) compared to Japanese (P < 0.001). The angle formed between occlusal plane and mandibular plane (OP-HP) was steeper in Japanese compared to Saudis.
Table 5 displayed cephalometric standards and student's t-test results for the Saudi and Japanese female subjects. Posterior cranial base (Ar-PTM) was smaller, whereas the anterior cranial base (PTM-N) was notably larger in Saudi adult female (P < 0.000).
Among horizontal skeletal relation, maxillary protrusion, and chin protrusion were slightly larger in the Saudi female group compared with the Japanese female (P < 0.01, and P < 0.003, respectively).
Alternatively, the Saudi adult female had significantly smaller upper posterior facial height (PNS-N), upper anterior facial height (N-ANS), lower anterior dental height (L1-MP), and lower posterior dental (L6-MP) compared to Japanese (P < 0.002, P < 0.000, respectively). The occlusal plane formed a more obtuse angle with the mandibular plane in Japanese women.
Discussion
The objectives of this study were to compare orthognathic cephalometric measurements of Saudi adults to African-American and Japanese adults using Burstone analysis for orthognathic surgery, in order to determine if significant (ethnic races) differences exist. The groups were also divided by sex to determine if significant sex differences exist between races.
The Saudi adult male and female had smaller posterior cranial base than the African-American. It is consistent with previous report (Flynn et al., 1989) of reduced posterior cranial base in African-American
compared to Caucasian. On the other hand, the anterior cranial base was significantly smaller in African-American male group compared to Saudi male. This finding was in agreement with D'Aloisio et al. (1992) and Jacobson (1978) who found that the anterior cranial base was smaller in Black American compared to Caucasian. The total cranial base was similar in the Saudi and African-American male groups, which was in agreement with Flynn et al.
(1989) who found no difference between African- Americans and Caucasians. The similarity in the length of total cranial base length might result from differences in the lengths of the anterior and posterior cranial bases. Saudi group had long anterior cranial base and short posterior cranial base, whereas the opposite was true for the Black American group.
Saudi female had larger anterior cranial base than African female but it is not significant. The total cranial base length was noticeably smaller for Saudi female group compared to African-American female group.
The present study results demonstrated significant differences in facial convexity between two comparisons. The Black American male and female displayed a significantly larger facial convexity than Saudi groups, which corresponded well with earlier findings (Flynn et al., 1989; Connor and Moshiri, 1985; Altemus, 1960; Cotton et al., 1951). In addition, African-American subjects showed greater maxillary skeletal prognathism than Saudi subjects, which agrees with previous studies (Flynn et al., 1989; Connor and Moshiri, 1985; Jacobson, 1978). In both sexes, the African-American had longer maxillary body length when compared with the Saudi sample values, which is consistent with previous studies (Flynn et al., 1989; Connor and Moshiri, 1985; Jacobson, 1978). The vertical relationship of the maxilla was significantly different between female groups. Saudi adult female had smaller upper posterior facial height and lower anterior facial height. This can be interpreted that the anterior part of the maxilla is rotated down (downward tipping).
Other investigators (Flynn et al., 1989; Connor and Moshiri, 1985; Jacobson, 1978) agreed that African- American have excessive vertical maxillary growth compared to Caucasians and hence to Saudi.
The vertical dental heights with its anterior and posterior component were smaller in Saudi than African-American subjects, which is in agreement with (Flynn et al., 1989). The form of the mandible revealed differences between Saudi and African- American groups. The total body length of the mandible was smaller in Saudi groups compared to African-American, which is consistent with earlier
adults. This finding was similar to Flynn et al. (1989) who found no difference between Black American and Caucasian. The gonial angle was larger in Saudi groups compared to Black American but this is not significant. The lower incisor proclination were greater in Black subjects compared to Saudi subjects, which was in agreement with previous study (Flynn et al., 1989; Jacobson, 1978; Altemus, 1960; Cotton et al., 1951).
The present study also shows distinct racial differences between Saudi and Japanese adults. The Saudi adult had smaller posterior cranial base and large anterior cranial base than Japanese groups.
However, total cranial base length showed no major difference. Alcalde et al. (1998) reported the same finding for the Japanese female. Their result showed that the Japanese female had a similar cranial base length as the Saudi female, but the pterygomaxillary fissure was located anteriorly, producing a shorter anterior cranial base. The majority of previous studies (Miyajima et al., 1996; Masaki, 1980; Nezu et al., 1982; Cooke and Wei, 1989) that compared the craniofacial morphology between Asian and Caucasians with Class I occlusion reported that Asians had a reduced anterior cranial base.
In this study, Saudi maxillary and chin position relative to the nasion perpendicular line demonstrated a more protruded position in both males and females compared with Japanese. These values were significant in the female group, but they are not significant with the Saudi male. These results suggested that the Saudi population had prognathic maxilla and prominent chin compared to Japanese population. Other Japanese studies (Alcadle et al., 1998; Miyajima et al., 1996; Ioi et al., 2007; Nojima et al., 2002) demonstrated that the Japanese had forward position of maxilla, and a slight retruded mandible and chin, indicating a more skeletal Class II tendency.
Considering the vertical dimensions, the Saudi sample had a significantly smaller upper anterior facial height in both sexes than Japanese. In addition the Saudi female showed significantly reduced upper posterior facial height. However, there was no difference in the lower anterior facial height between Saudi and Japanese female groups. The interpretation of the findings suggested that Saudi had reduced facial height compared to Japanese, but this characteristic appears to be more significant in female than males. This finding support the result obtained by Alcalde et al. (1998)and Nezu et al. (1982) who concluded that the Japanese have longer faces. The
of Japanese. These differences might be attributed to the reduced facial height in Saudi adult. A similar result was seen by other studies (Ioi et al., 2007;
Alcalde et al., 1998; Engel and Spolter, 1981).
Considering the mandibular dimensions were smaller in Saudi adults compared to Japanese but not significant, except for mandibular ramus length and gonial angle showed significant differences. Saudi male subjects had reduced mandibular ramus length compared to Japanese, which might contribute to the reduction in facial height. However, the gonial angle in Saudi groups male was significantly larger than Japanese groups. The disparity of this study found in the gonial angle between the two groups was in conflict with Alcadle et al. (1998). This is most likely due to error in landmark identifications. Points located on poorly defined outline or low contrast such as Articularie and Gonion had a significant error method as stated by Grybauskas et al. (2007).
Dento-alveolar comparison indicated that the lower and upper incisors in Saudi adult were less protruded than those in Japanese; it is more evident in male Saudi group. Similar findings by Miyajima et al.
(1996), Engel and Spolter (1981), and Nojma et al., (2002) who reported that the Japanese sample had a more dental protrusion compared to Caucasians. The occlusal plane to horizontal plane angle was significantly reduced in the Saudi adults; it might be associated with reduced facial height. However, the Japanese male and female had steeper occlusal plane, which agree with Alcalde et al. (1998) findings.
In view of the findings of the current study, there are fundamental variations in the craniofacial structure of Saudi adult compared to African- American and Japanese. The findings of this study support the premise that a single standard of cephalometric norms is not appropriate for application to diverse racial and ethnic groups.
Additional research on the issue of soft tissue analysis of well-balanced profile in Saudi adults appears to be warranted. Further study is required to confirm this result on the Saudi population using a larger sample size, which can be a true representative sample across the entire Saudi population.
Conclusion
The major craniofacial differences between Saudi adult and African-Americans were as follows, Saudi adult had significantly: (1) increased anterior cranial base, and reduced posterior cranial base, (2) reduced facial convexity, maxillary protrusion, and maxillary
length, (3) smaller upper posterior facial height, lower anterior facial height, and downward tipping of maxilla, with adult female subjects, (4) Smaller vertical dental heights, (5) smaller total body length of mandible, and (6) less proclination of lower incisors.
Saudi adult compared to Japanese had significantly: (1) increased anterior cranial base, and reduced posterior cranial base, (2) prognathic maxilla and prominent chin in females, (3) smaller upper anterior facial height in both sexes, (4) significantly reduced upper posterior facial height with Saudi female subjects, (5) smaller vertical lower dental heights, (6) smaller ramus and obtuse gonial angle in males, (7) less proclination of upper and lower incisors, and (8) less steep occlusal plane to horizontal plane.
These differences between Saudi subjects with Black Americans and Japanese might represent true differences in skeletal and dental features between the three racial groups, or could simply reflect the nature of the samples. So, further investigation on this area is required.
Acknowledgement. Authors would like to express their appreciation to Dr. Naser Mefleh for his help and advice in the statistical analysis.
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